03/30/2014 at 01:00 PM EDT
stepped into the spotlight Saturday night, the first time since completing a rehab program
for eating disorders
The singer, 27, attended the Humane Society of the United State's 60th anniversary benefit gala in Beverly Hills, and posed for photos in a sheer black floor-length gown and her signature multi-colored hair, chopped into a wavy bob.
"She was clearly enjoying being back on the red carpet," says an onlooker. "She looked great … very healthy."
Since leaving rehab earlier this month, Kesha has made some changes
, like updating her Twitter handle
, dropping the dollar sign from her name and severing ties with those who don't encourage her wellness.
"She has eliminated all of the negative people and influences in her life," a friend of the pop star told PEOPLE. "She has surrounded herself with only supportive and loving friends and family."
"She's doing great. She looks and feels fantastic," a friend says
The singer delayed her tour
in February while she continued treatment at a Chicago-based facility, after beginning treatment for anorexia and bulimia in January.
Reporting by MELODY CHIU